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Originally Posted by M3SQRD
Oops… I had SPM listed incorrectly as 2:21-1:22 when it should’ve been 1:21-1:22. Fixed. Thanks!
Only one high speed braking zone doesn’t necessarily mean it’s harder on the brakes. SPM has four significant brake zones, one is going downhill as you brake with a delta of 70+ mph so your weight is working against you making it more demanding, a front straight with speeds of 140+ mph and a corner with a 40+mph braking delta on a 2.0 mile track. VIR has two ~150 mph braking zones and four moderate-high delta braking events on the Full 3.29 mile course.
It is relevant because I’m hitting higher speeds, therefore, higher kinetic energy being converted to brake rotor thermal energy (heat) and only the rear and trunk interior have been removed plus a welded-in roll bar was added. There’s about a 120 lbm net reduction. Also, I’m at full weight in my e92 M3s on both tracks with similar lap times (about 1 sec delta) and the same brake compounds in the Z31/Z31 calipers. I see far less brake wear on the same pad compounds and same pad thicknesses (except PFC Z54/Z45 but that’s only used PFC pad compounds with very low pad wear and long rotor life that lasts a full track season). Something is causing your accelerated pad wear. Have you measured rotor and caliper temperatures? Your comment about xp20 fading after a couple of laps means you’re exceeding 2000 deg F on the pad! SRF is good but I prefer PFC and AP brake fluid. BMW switched to low-viscosity brake fluid. Brake fluid like PFC and AP have lower viscosity at high temperatures which more closely matches the viscosity of low-viscosity brake fluid. This means if the viscosity at track temperature is different from the viscosity of low-viscosity brake fluid, the ABS, MDM (if using) and DSC (if using) may not perform properly. SRF has different viscosity properties.
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BFR has two back to back high speed braking zones. again, I don't want to make it sound like my driving style doesn't contribute to the high wear rate, I'm sure it does. But that track *does* have a rep for being tough on brakes.
I went with Motul 660 on the G82 because I didn't like the pedal feel of SRF (which is funny because the G82 is brake by wire so it wouldn't impact pedal feel there at all, but whatever)
Quote:
Originally Posted by BoilerUP
Longer courses can also mean longer, higher speed straights...which means more airflow for cooling things down.
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correct. more airflow, and more time. that's why road america, despite being fast with 3 separate 140+ -> 40-50 brake zones isn't as hard on brakes because there's much more time and airflow to cool them down.